In known processes, articles are painted by application of powder to an article to be painted which is then passed through a pointing room. This method of paint application obviously involves considerable loss of paint, including, but not limited to paint deposited on the walls and the floor of the painting room.
These paint deposits must be continuously eliminated in order to avoid frequent interruption of the operation of the room necessary to permit long and tedious cleaning of the walls and floor of the room to be carried out, particularly by scraping off of the deposited paint. To prevent the formation of these deposits, air charged with droplets of paint is forced into the room across a scrubber provided with a curtain of scrubbing liquid, so that these droplets are transferred from the air to this liquid. The liquid, charged with the paint picked up thereby, flows through one or more channels placed beneath the room to a collection tub or basin wherein the paint is separated from the scrubbing liquid, the latter being recycled into the room to feed the scrubber.
The scrubbing liquids which are most often used in such processes are constituted by a solution of chemical products which have an alkaline reaction with water, and the liquids which are then obtained are used to denature the collected paints, in other words, to cause the paints to lose the adhering power thereof and thus enable ready separation of the paints from the remaining liquid. This is traditionally followed by a separation of the scrubbing liquid and the collected paint in the collection tub, so as to enable recycling of the scrubbing liquid as mentioned above. According to whether the collected paint floats to the surface of the tub or decants at the bottom, the next step is either a separation step comprising skimming of the surface or a separation step involving scraping of the bottom of the tub by appropriate known devices.
Different types of alkaline or neutral denaturant compositions are known, including, but not being limited to, the following:
organic solvents (aliphatic or aromatic hydrocarbons, alkyl-ketones); and
nonionic moistening or emulsifying agents (ethylene and alcohol oxides and alcohols or phenol-alkyls, for example).
Scrubbing liquids are also known wherein clays, such as bentonite, are added to overcome the adhering power of the paint and to increase the dispersion thereof.
A further method or process is known which provides for precipitation of lacquers of synthetic resin base using water as scrubbing liquid, made of alkaline and containing an additive constituted of an aqueous dispersion of wax, providing coating of the droplets with lacquer.
These known compositions of scrubbing liquids give satisfactory results with traditional paints, such as glycerophthalic and acrylic paints and finishes. The adhering power of such paints is reduced but, in the scrubbing liquid collection tub, a part of the paint floats to the surface, a part decants, and a part remains in suspension in the liquid phase, and this makes it difficult to collect the paint and to clean the scrubbing liquid.
Presently, in the automobile paint industry, new types of paints are used to limit release of organic solvents into the atmosphere. Such paints can include paints with a high dry portion, polyester paints, and paints including two compounds. These paints are very difficult to denature, which leads users of paint rooms to increase the concentration of chemical products in the scrubbing liquids. As a result, it is not unusual to have scrubbing liquids which are so charged with soluble organic materials that they cannot be recycled, thereby obligating the user to discard all of the liquid. Moreover, because these types of paint are difficult to denature, and thus the paint rooms become rapidly caked with the paints, users of such paints are required to undertake frequent, time consuming, tedious and onerous cleanings.